Turkish President Recep Tayyip Erdogan condemned the German economy minister's warnings to not invest in Turkey, and said that Germany needs to "pull itself together".

Speaking in Istanbul, Erdogan said, "You [Germany] are not strong enough to defame Turkey and you are never strong enough to scare us with such [threats]."

Turkish President Tayyip Erdogan condemned comments by Germany's economy minister on Friday warning companies off investing in Turkey, as the dispute between the NATO allies continues to simmer.

"I see some people mixing up trade and politics. I strongly condemn the comments of the German Minister. Turkey's doors remain wide open to foreign investment, including German investment," he said in a speech in Istanbul.

Turkey's minister of economic affairs, Nihat Zeybekci also sought to stem the economic fall-out from a growing diplomatic crisis with NATO ally Germany, saying that German investments in Turkey were fully guaranteed by both the Ankara government and its laws.

"100 percent" guaranteed

In an interview with Reuters, Zeybekci also denied reports that Turkey gave Berlin a list of companies it was targeting for suspected links to last year's coup attempt.

"All German investments in Turkey are 100 percent under the guarantee of the Turkish government, the state and law," he said in the interview in Ankara late on Thursday.

"The Turkey-Germany crisis is temporary. One must refrain from words that would cause lasting harm to the economies. Germany must reassess comments that are inappropriate."

Turkish Prime Minister Binali Yilidirm also dismissed comments by German authorities that he said were aimed at sowing doubt among investors, adding that Turkey was just as safe as Germany.

Germany was Turkey's top export destination in 2016, buying $14 billion worth of Turkish goods, according to IMF data. It was also the second biggest source of Turkish imports, at $21.5 billion. Only China, at $25.4 billion, exported more to Turkey.

"Fake news"

The Die Zeit newspaper reported this week that Turkish authorities had several weeks ago handed Berlin a list of 68 German companies, including Daimler and BASF that they accused of having links to US-based cleric Fetullah Gulen, blamed by Ankara for orchestrating last July's failed coup.

But Turkey's deputy prime minister, Mehmet Simsek, said on Twitter on Thursday that the report was "completely false."

Press reports that Turkey is investigating Daimler AG and BASF SE are completely false. We welcome German investors. https://t.co/Wt1Ya6fEbG

A German security force said on Friday Turkey has provided German authorities with a list of over 680 German firms it suspects of supporting terrorism, ten times the number initially reported by German media.

But Zeybekci also rejected such claims, calling them "fake news."

"The allegation that Turkish authorities gave Germany the names of German companies linked to Gulen is not true. This is fake news," Zeybekci said.

Before the failed coup and the massive crackdown which followed, members of Gulen's movement were accused of running a parallel shadow government after gaining control of state institutions which included the military and the judiciary.

Rights groups and some Western governments say Erdogan is using the crackdown as a pretext to quash dissent. The Turkish government says the measures are necessary given the gravity of the security and terrorism threat it faces.

Turkey designated Gulen's movement as a terrorist organisation in 2015, using the acronym FETO, for Fetullah Terrorist Organisation.

Travel warnings

Germany has also issued a travel warning for its citizens coming to Turkey after the arrest of human rights activists in Istanbul.

Turkey says the arrested members of Amnesty International were involved with terrorism, a charge Germany denies.

The German foreign minister says the detention is disproportionate and unlawful, while Turkey says Germany should avoid politicising a legal issue.